1. Field of the Invention
The present invention relates to a stepping motor control device, an optical apparatus, a stepping motor control method, and a non-transitory computer readable recording medium, and more specifically to a stepping motor control device including a position sensor configured to detect the position of a rotor.
2. Description of the Related Art
A stepping motor is rotatable in steps of a predetermined angle due to the switching of energization of a coil, and thus has a feature of being easily position-controllable without using a position sensor. Because of this feature, a drive mode using open-loop control, in which the state of energization of a coil is switched in accordance with a determined time interval, is generally used. However, there may be a problem in that when the motor is driven at a high speed or when a large load is imposed on the motor, the rotor may not be responsive to the switching of energization of a coil and an out-of-step condition will be prone to occur.
To address this problem, a stepping motor which is switchable to a drive mode which provides high-speed driving through feedback control in which the state of energization of a coil is switched for acceleration or deceleration in accordance with the output of a position sensor configured to detect the position of the rotor is available. In addition, a stepping motor which uses open-loop control and feedback control in combination so that the stepping motor is driven using the open-loop control at low speeds and is driven using the feedback control at high speeds is also available. Thus, it is possible to accurately control the driving of a stepping motor in a low-speed region and a high-speed region.
The relationship between the torque produced by a motor and the rotation speed of the motor is referred to as “T-N characteristics”. The T-N characteristics vary depending on the voltage applied to the motor, that is, the voltage across the terminals of a coil. As the voltage increases, the torque produced increases, allowing the motor to rotate at a high speed.
Japanese Patent Laid-Open No. 62-285695 discloses a stepping motor drive control device including an encoder for detecting a rotation angle. A memory in the drive control device stores in advance correspondence data between voltages applied to the motor and rotation speeds of the motor. Accordingly, it is possible to easily determine the value of a voltage to be applied to the motor to make the motor reach the target rotation speed. The control device can reduce the variations of the load on the motor, and can provide accurate control of acceleration and deceleration of the motor.
Japanese Patent Laid-Open No. 10-150798 discloses a drive control method for providing high-speed, high-accuracy rotation of a motor by applying a current having a square driving waveform to the motor in feedback control.
In a case where a stepping motor is mounted in an optical apparatus such as an image capturing apparatus, it is desirable to rapidly move a member included in the optical apparatus and to reduce variations in the speed of the member in order to improve the operability and functionality of the optical apparatus.